1. Field of the Invention
The present invention relates to a focal-plane shutter apparatus in a camera.
2. Related Background Art
FIG. 1 shows a camera having a conventional focal-plane shutter apparatus, in which numeral 1 denotes a front panel member on which a lens fitting mount 2 is formed.
A mirror box 3 is located behind the front panel member 1.
The mirror box 3 has a side face base plate 4 and a side-and-lower face base plate 5. A movable mirror 6 is located between these base plates 4 and 5.
Also, light shield sheets 7 and a light shield plate 8 are located in the mirror box 3.
The mirror box 3 is structured to be connected by an upper fixing member 9. Above the mirror box 3, there is a holding member 10 located for attachment of a finder optical system.
A focal-plane shutter apparatus 11 is located behind the mirror box 3.
The focal-plane shutter apparatus 11 has a first plate 12 and a second plate 13 located at a predetermined spacing to face each other. A vane group 14 comprising a plurality of light shielding thin plates is contained between the first plate 12 and the second plate 13.
A vane group drive mechanism 15 for driving the vane group 14 is located in front of the first plate 12.
FIGS. 2 and 3 show the focal-plane shutter apparatus as disclosed in Japanese Utility Model Application Laid-open No. 63-45540, in which the vane group 18 is contained between the first plate 16 and the second plate 19.
In this focal-plane shutter apparatus, the first plate 16 is formed of a resin, and support shafts 17 of the vane group drive mechanism are integrally formed of the resin on the first plate 16.
Since the first plate 16 is made of the resin in such a focal-plane shutter apparatus, a reduction in weight of the focal-plane shutter apparatus may be attained.
There are, however, following problems recognized in such a focal-plane shutter apparatus, because the support shafts 17 of the vane group drive mechanism is integrally formed with the first plate 16 made of the resin. It is difficult to attain a sufficient precision, because a precision of relative position of the support shafts 17 is determined by a molding precision. It is also difficult to attain a sufficient precision because the relative position of the support shafts 17 changes depending upon a deformation due to a temperature of the first plate 16. Thus, an enough reliability cannot be provided for a high speed shutter apparatus requiring a specifically high precision.
Further, since the support shafts 17 are fixed to the first plate 16, members constituting the vane group drive mechanism have to be assembled about the support shafts 17, which is inferior in assembly operability of the vane group drive mechanism to the first plate 16 and which necessitates a great number of man-hours for assembly.
Also, in the conventional shutter apparatus, the shutter drive mechanism is assembled with reference to a support shaft or shutter drive shaft fixed on the first plate or shutter base plate, and a mirror drive mechanism and an aperture drive mechanism are assembled with reference to a mirror drive shaft fixed on the side face base plate forming the mirror box.
The mirror drive mechanism also serves as a shutter charge mechanism of the shutter drive mechanism. Thus, in assembly, the two drive mechanisms are assembled taking into consideration a relative position relation between them in operation.
In the conventional shutter apparatus, when the shutter drive mechanism is mounted on the shutter base plate, a mounting position of the shutter drive mechanism must be determined with respect to the center of optical axis. Also, when the mirror drive mechanism is mounted on the mirror box, a mounting position of the mirror drive mechanism must be determined with respect to a direction of a short side of the shutter base plate and to a direction of the optical axis.
In spite of a fact that the mirror drive mechanism also serves as the shutter charge mechanism of the shutter drive mechanism, the respective drive mechanisms are independently mounted onto the mounting base plate in assembly. Such assembly makes it difficult to achieve a desired precision of relative position between the two drive mechanisms, which makes the assembly operation of the apparatus very difficult and therefore consumes the time.
Further, preparing for a case that a slight deviation is caused in relative position of the two drive mechanisms, a space is necessary to absorb the deviation in operation of the drive mechanisms, in respect of designing of the mechanisms. Such a space is a hindrance for reduction in size of the apparatus, for reduction in energy to operate the drive mechanisms, and for reduction in operation time.
Further, the shutter apparatus must be arranged in structure such that the shutter drive shaft is perpendicular to the mirror drive shaft or the aperture drive shaft. However, in an apparatus in which the mirror box and the shutter base plate are integrally formed with each other as in one embodiment of the present invention, it is impossible that the two drive shafts are fixed on the mounting base plate perpendicular to each other. Thus, it is naturally impossible that the shatter drive mechanism and either the mirror drive mechanism or the aperture drive mechanism are individually mounted.
A slight deviation of mounting position of the shutter drive mechanism and either of the mirror drive mechanism and the aperture drive mechanism in the direction of optical axis and in the direction of a long side of the shutter base plate (in the horizontal direction) causes no substantial influence on a control upon actual driving of the shutter and either the mirror or the aperture.
It is because the drives of the shutter and either the mirror or the aperture are carried out in the direction of the short side of the shutter base plate (in the vertical direction). Therefore, the most important point in respect of the mounting position is a position in the vertical direction.